def main():
    K = int(input())
    
    a_i = 7
    if a_i % K == 0:
        print(1)
        return

    for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
    print(-1)

main() def main():
    K = int(input())
    
    a_i = 7
    if a_i % K == 0:
        print(1)
        return

    for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
    print(-1) main K = int(input()) K int(input()) int input() input a_i = 7 a_i 7 if a_i % K == 0:
        print(1)
        return

     a_i % K == 0 a_i % K a_i K 0 print(1) print 1 return for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
     i range(2, 10 ** 6+1) range 2 10 ** 6+1 10 ** 6 10 6 1 a_i = a_i * 10 + 7 a_i a_i * 10 + 7 a_i * 10 a_i 10 7 if a_i % K == 0:
            print(i)
            return
         a_i % K == 0 a_i % K a_i K 0 print(i) print i return a_i %= K a_i K print(-1) print -1 main() main def main():
    K = int(input())
    
    a_i = 7
    if a_i % K == 0:
        print(1)
        return

    for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
    print(-1) def main():
    K = int(input())
    
    a_i = 7
    if a_i % K == 0:
        print(1)
        return

    for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
    print(-1) main
def main():
    K = int(input())
    
    a_i = 7
    if a_i % K == 0:
        print(1)
        return

    for i in range(2, 10 ** 6+1):
        a_i = a_i * 10 + 7
        if a_i % K == 0:
            print(i)
            return
        a_i %= K
    print(-1)

main()
